Typical large-scale offshore wind farm architectures include a plurality of wind turbines, along with generators and collection networks, for collecting the generated electricity and transmitting it to shore, e.g., via high-voltage DC, HVDC, or high-voltage AC, HVAC, transmission systems. The choice of HVAC or HVDC transmission depends mainly on the distance from the offshore wind farm to the onshore grid connection point.
The use of low-frequency AC, LFAC, transmission at high voltages to the onshore grid connection point has also been considered. While LFAC transmission from the offshore wind farm requires additional frequency conversion equipment at the onshore grid connection point, its usage can extend the economic distance of HVAC connections between the offshore wind farm and the onshore grid connection point.
In a known approach to low-frequency collection and transmission of electricity in offshore wind farms, low-speed generators produce AC outputs with a nominal frequency of 16.7 Hz or 20 Hz. The generated electricity is coupled into the LFAC transmission system using one or more boost transformers. However, it is recognized herein that this approach suffers from a number of disadvantages, including necessitating the use of undesirably large equipment.